The present invention relates to a screw and, more particularly, to a screw suitable for using in wood, construction materials, and similar materials.
A large amount of wood or compound wooden materials mixed and compressed from plastic resin and wood chips are used to produce wooden work-pieces for furniture, decoration and construction, and screws are often used in connection between wooden work-pieces.
A conventional screw 10 for using with wood plank is shown in FIG. 1. The screw 10 includes a round shank 12 and a screw thread 14 disposed on the shank 12. The shank 12 includes an insertion tip 16 and a head end 17. The insertion tip 16 has an end cutting groove 18, and a plurality of ribs 19 protrudes from the head end 17. When the insertion tip 16 of the screw 10 penetrates a plank (work-piece) to be connected, the plank is cut by the end cutting groove 18 and screwed by the screw thread 14 until the head end 17 is embedded into the plank in which a drilled hole is expanded by the plurality of ribs 19.
However, the end cutting groove 18 of the screw 10 extends axially along the shank 12 which makes it difficult for wood chips produced from cutting to be expelled smoothly. Therefore, the screw 10 will be easily obstructed by the waste chips during the process of screwing into the plank, which will require more effort in operation, and the plank will easily crack because of compression. Moreover, the surface flatness of the plank is worsened because the waste chips is released from the drilled hole and left on the plank which is being penetrated by the screw 10. Furthermore, the screw thread 14 in FIG. 1 is forward screwed in the plank without anti-pull-out and anti-screw-out properties. Thus, two planks joined with the screws 10 may teeter when the screws 10 under effects of vibrations or other factors are loosened in a pull-out direction.